Fig. 8
Mechanism underlying the laser-induced currents. a–f Laser-dressed single-particle eigenstates of SiO2 (N = 6, E || a, μF = 6.0 eV) for different laser field amplitudes. The plots show the eigenenergies and probability density distribution of the eigenstates along the junction. In each unit cell, the population of each eigenstate is divided into a contribution due to the Wannier functions that form the VB (blue) and CB (red). For a given E(t), current can only flow through the junction when the Wannier-Stark states at the terminal ends are properly energetically aligned with the lead’s chemical potential. Specifically, the terminal Wannier functions associated with the CB (or VB) need to be below (or above) the chemical potential for silica-metal charge exchange. The blue arrows indicate the flow of electrons. Only for E > 1.4 V Å−1 transport channels are open and significant current can be observed. g Currents entering the left (IL, black) and right (IR, red) contact during the photoinduced dynamics of the junction induced by E(t) with φ = π (in gray). The main plot shows the contribution due to the CB to the total current (electron transport) and the top-right inset that of the VB (hole transport). The energies and spatial probability distribution of the laser-dressed eigenorbitals for maximum and minimum laser amplitude are shown at the top-left and bottom-right corners, respectively. Net phase-controllable currents arise due to a difference in effective coupling between SiO2 and the metallic contacts for negative and positive field amplitude. In the CB, a burst of charge from the metal is observed around the central peak of the pulse for positive amplitude where charge injection is allowed. By contrast, for negative amplitudes transport through the CB is energetically blocked, leading to net charge transport
